Field of the Invention:
The present invention relates to a hearing aid system that includes a first hearing aid and a second hearing aid. The first hearing aid has a first acousto-electric converter and the second hearing aid has a second acousto-electric converter. The converters are configured to convert incoming acoustic signals into first and second electrical signals. Furthermore, the hearing aid system has a signal processing unit, wherein the signal processing unit has a signal link with the first and the second acousto-electric converters.
Hearing aids are wearable hearing apparatuses which are used for providing care for the hard of hearing. In order to meet the numerous individual needs, different designs of hearing aids such as behind-the-ear hearing aids (BTE), hearing aids with an external earpiece (RIC: receiver in the canal) and in-the-ear hearing aids (ITE), for example also concha hearing aids or completely-in-canal hearing aids (ITE, CIC), are made available. The hearing aids cited by way of example are worn on the outer ear or in the auditory canal. In addition, bone conduction hearing aids, implantable or vibrotactile hearing aids are however also available on the market. In this situation the stimulation of the damaged hearing takes place either mechanically or electrically.
In principle, hearing aids have as their essential components an input converter, an amplifier and an output converter. The input converter is as a rule an acousto-electric converter, for example a microphone, and/or an electromagnetic receiver, for example an induction coil. The output converter is implemented for the most part as an electroacoustic converter, for example a miniature loudspeaker, or as an electromechanical converter, for example a bone conductor. The amplifier is usually integrated in a signal processing unit.
It is known that hearing with two ears enables a person to more easily understand speech in background noise or in an echoey environment. Furthermore, binaural hearing is a primarily important prerequisite for spatial hearing and sound wave localization. Because of the significance of the binaural processes in the analysis of hearing situations it is understandable that hearing impaired persons benefit more from two hearing aids for a binaural fitting than from one single hearing aid for a monaural fitting.
The binaural signal processing reacts particularly sensitively to differences between the signals because the natural variations in the signals from both sides of the head differ only slightly in their amplitude, phase and/or frequency distribution. It is therefore in particular important that deviations are not artificially added by the signal processing in the hearing aids. In this situation the microphones first and foremost are particularly susceptible because small mechanical manufacturing tolerances can result in large deviations on account of their small dimensions. For the same reason the properties may also change during actual operation, for example as a result of contamination or material ageing. Since this effect mostly occurs unsymmetrically the impact is particularly serious.
Pairs of microphones which have almost identical properties are therefore normally assembled together during the production process. This process is however elaborate and does not prevent changes during operation.
U.S. Pat. No. 8,588,441 B2 and its counterpart European published patent application EP 2 360 951 A1 describe that, for microphones which have matching properties in a frequency range, the direction of a source is determined in that frequency range. By means of said identified source having a predefined direction it is then possible to acquire and compensate for deviations in other frequency ranges.
It is known from U.S. Pat. No. 7,340,231 B2 and its counterpart international patent application publication WO 2003/032681 A1 that hearing aids recognize the voice of the wearer in order to process it with changed parameters compared with other tones and thus to convey to the wearer of the hearing aid a familiar sound of the wearer's own voice. To this end U.S. Pat. No. 7,512,245 B2 specifies different possible ways of recognizing the wearer's own voice.
However, the problem remains that differences in the microphone properties which arise during operation are not compensated for.